This invention relates generally to the field of additive manufacturing. In particular, the present invention relates to the feed material used to create additively manufactured articles.
Additive manufacturing is an established but growing technology. In its broadest definition, additive manufacturing is any layerwise construction of articles from thin layers of feed material. Additive manufacturing may involve applying liquid, layer or powder material to a workstage, then sintering, curing, melting, and/or cutting to create a layer. The process is repeated up to several thousand times to construct the desired finished component or article.
Various types of additive manufacturing are known. Examples include stereolithography (additively manufacturing objects from layers of a cured photosensitive liquid), Electron Beam Melting (using a pulverant material as feedstock and selectively melting the pulverant material using an electron beam), Laser Additive Manufacturing (using a pulverant material as a feedstock and selectively melting the pulverant material using a laser), and Laser Object Manufacturing (applying thin, solid sheets of material over a workstage and using a laser to cut away unwanted portions). Each method has advantages and disadvantages. For example, one disadvantage of Laser Additive Manufacturing is that as pulverant material is made from increasingly fine particles as required for ever-thinner layers, the pulverant material may begin to clump, and the increased surface area to volume ratio of finer particles results in higher oxidation rates.
Non-additively manufactured production parts can be traced to an original forged billet, a pour of metal at a foundry, or to the original sheet metal. It is not as easy to trace the pedigree of parts built by additive manufacturing. Economically it is unlikely that production parts will be built of a virgin material. Building five pounds of product may require one hundred pounds of powdered starting material. It is likely that the product will be built from a mixture of virgin material, previously used, recycled, or reprocessed metal powder. Powdered metals are prone to contamination through oxidation, humidity, and any remnants of a previous build. This creates a problem of documenting the condition/properties of the powdered metal used to build the end material.